Method and apparatus for regulating transmembrane ion movement

ABSTRACT

An improved apparatus and method for regulating transmembrane ion movement through a biochemical membrane. The apparatus includes a magnetic field generator and a magnetic field detector for producing a controlled, fluctuating, directionally oriented magnetic field parallel to a predetermined axis projecting through the membrane. The field detector samples the magnetic flux density along the predetermined access and provides a signal to a microprocessor which determines the average value of the flux density. This ratio is maintained by adjusting the frequency of the fluctuating magnetic field and/or by adjusting the intensity of the applied magnetic field as the composite magnetic flux density changes in response to changes in the local magnetic field to which the target membrane is subjected. By maintaining these precise predetermined ratios of frequency to average magnetic flux density, ion transport is controlled.

This application is a continuation-in-part of U.S. patent applicationSer. No. 923,760, filed Oct. 27, 1986, entitled "Techniques forEnhancing the Permeability of Ions Through Membranes", which isexpressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to the transmembrane movement ofions and to oscillating magnetic fields. More specifically, the presentinvention relates to an improved method and apparatus for regulating thetransmembrane movement of ions across biochemical membranes such as cellmembranes. In the inventive method and apparatus, a predeterminedresonance condition for a preselected ion is maintained at a constantvalue, notwithstanding changes in the local magnetic field componentalong a predetermined axis such that transmembrane movement of the ionis regulated.

BACKGROUND OF THE INVENTION

The inventors of the present invention devised a method and apparatusfor regulating the transport of a preselected ion across a cell membraneutilizing an applied, oscillating magnetic field. This remarkableachievement is disclosed in U.S. patent application Ser. No. 923,760entitled, "Techniques for Enhancing the Permeability of Ions", which wasfiled on Oct. 27, 1986, and the disclosure of which is incorporatedherein by reference. Therein, a method and apparatus are disclosed bywhich transmembrane movement of a preselected ion is magneticallyregulated using a time-varying magnetic field tuned to the cyclotronresonance energy absorption frequency of the preselected ion. Thisimportant discovery brought to light the interplay of local magneticfields and the frequency dependence of ion transport mechanisms.

Having established a method by which selective ion transport can beregulated, the present inventors discovered that certain characteristicsof living tissue could be controlled by application of an oscillatingmagnetic field having a non-zero average value. Significantly, it wasdetermined that selected ratios of the frequency of the applied field tothe flux density of the total magnetic field passing through the tissuealong a predetermined axis were capable of stimulating the growth anddevelopment of the target tissue. This was demonstrated to be effectivein promoting the growth of bone tissue. As a result, U.S. patentapplication Ser. No. 172,268, entitled "Method and Apparatus forControlling Tissue Growth with an Applied Fluctuating Magnetic Field"was filed on Mar. 23, 1988, the disclosure of which is incorporatedherein by reference.

Therein, there is provided an apparatus for controlling the growth ofliving tissue. The apparatus includes magnetic field generating meanssuch as a field coil for generating a controlled, fluctuating magneticfield which penetrates a tissue, and an associated magnetic fieldsensing device for measuring the intensity of the magnetic field presentin the tissue. In one embodiment, the magnetic field generating meansand magnetic field sensor are enclosed within a housing along with apower source.

The work with tissue growth control was extended and it was discoveredthat tissue development can be regulated to control the growthcharacteristics of non-osscous, non-cartilaginous connective tissueproper and cartilaginous tissue. These inventions are disclosed,respectively, in U.S. patent application Ser. No. 254,438, entitled"Method and Apparatus for Controlling the Growth of Non-Osseous,Non-Cartilaginous Solid Connective Tissue", which was filed Oct. 6,1988, the disclosure of which is incorporated by reference, and in U.S.patent application Ser. No. 265,265, entitled "Method and Apparatus forControlling the Growth of Cartilage", which was filed Oct. 31, 1988, thedisclosure of which is incorporated by reference.

The inventors have now discovered that by using a feedback system tomonitor the local field component of the composite magnetic field, theapplied component can be automatically adjusted to maintain the properbalance to bring about transmembrane movement of ions in any applicationof ion transport tuning.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides an apparatus forregulating the transmembrane movement of ions across a biochemicalmembrane such as a living cell membrane which includes magnetic fieldgenerating means, an associated magnetic field sensing means, and meansfor automatically adjusting the flux density of the magnetic fieldgenerating means to compensation for any deviation of the average valueof the composite magnetic field intensity from a set point magnetic fluxdensity as measured by the magnetic field density means.

In operation, the magnetic field generating means is positioned adjacenta predetermined space containing a biochemical membrane in the presenceof a preselected ion to be transported. A fluctuating, directionalmagnetic field is then generated by the magnetic field generating means.The applied magnetic flux density is directed along a predetermined axiswhich passes through the membrane. In one embodiment, the appliedmagnetic flux density along the axis is superimposed on that componentof the local or ambient magnetic field which is parallel to thepredetermined axis to create a fluctuating composite field. Theresultant combined magnetic flux density which is parallel to thepredetermined axis and which passes through the membrane is measured bythe magnetic field sensor. The magnetic field sensor determines the netaverage value of the magnetic flux density which passes through themembrane along the predetermined axis. In one embodiment, the frequencyof the fluctuating magnetic field is set at a predetermined value andthe net average value of the magnetic flux density is then regulated byadjusting the magnitude of the applied magnetic field to produce acombined magnetic field having a preselected ratio of frequency-to-fieldmagnitude which causes transmembrane movement of the preselected ionthrough the membrane. In a preferred embodiment, changes in themagnitude of the local magnetic field along the predetermined axis whichwould otherwise alter the magnetic flux density of the combined magneticfield parallel to the predetermined axis, and which would thus produce adeviation from the desired ratio, are counterbalanced by adjustment ofthe magnitude of the applied, fluctuating magnetic field. Thisadjustment is preferably made by microprocessing means in associationwith both the magnetic field generating means and the magnetic fieldsensor. Preferred ratios of frequency-to-field magnitude are determinedwith reference to the equation:

    f.sub.c /B=q/(2 πm)

where f_(c) is the frequency of the combined magnetic field in Hertz, Bis the non-zero average value of the magnetic flux density of thecombined magnetic field parallel to the axis in Tesla, q/m is inCoulombs per kilogram and has a value of from about 5×10⁵ to about100×10⁶. B preferably has a value not in excess of about 5×10⁻⁴ Tesla.In one embodiment, the values of q and m are selected with reference tothe charge and mass of a preselected ion.

In another embodiment, changes in the ambient magnetic field which wouldotherwise alter the ratio of frequency-to-magnetic field arecounterbalanced by adjusting the frequency of the applied magnetic fieldto maintain the preferred ratio. The present invention also contemplatesthe adjustment of both frequency and field magnitude to maintain thepredetermined preferred ratio. Preferably, the peak-to-peak amplitude ofthe AC component is in the range of about 2.0×10⁻⁷ to about 2.0×10⁻⁴Tesla. The waveform is preferably substantially sinusoidal, but otherwaveforms are suitable.

In another aspect, the present invention provides a method ofcontrolling the transmembrane movement of ions across a biochemicalmembrane including the steps of generating a fluctuating,directionally-oriented magnetic field; positioning a biochemicalmembrane and a preselected ion to be transported within the fluctuating,magnetic field so that the field passes through the membrane parallel toa predetermined axis that extends through the membrane; measuring thenet average value of the combined magnetic flux density parallel to thepredetermined axis through the membrane, where the combined magneticfield is the sum of the local magnetic field along the predeterminedaxis and the applied magnetic field; and automatically adjusting thefrequency and/or magnitude of the applied magnetic field to produce acombined magnetic field along the axis having a predetermined ratio offrequency-to-magnitude, where the predetermined ratio causestransmembrane movement of the preselected ion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, perspective view of an exemplary living celllocated in a bounded active volume in a space defining a rectangularcoordinate axis system and subjected, within this active volume, to amagnetic flux density created by an electrical coil, or an equivalentpermanent magnetic array or any other equivalent source of magnetic fluxdensity.

FIG. 2 illustrates the fluctuating, non-zero average value of thecombined magnetic flux density.

FIG. 3 is a block diagram of an embodiment of the present invention inwhich the circuit of the inventive apparatus is arbitrarily divided intoconvenient functional sections.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1 of the drawings, ion transport apparatus 100 of thepresent invention includes coils 102 and 104 of a Helmholtz coil pairarranged to generate an applied magnetic field directed along alongitudinal axis identified by the letter Z. The number of turns N, thediameter of the coils, the separation of the coils, and the wire gaugeare only critical insofar as conventional practice requires constraintson these and other design parameters to allow optimal performancecharacteristics in achieving predetermined flux densities as required inthe preferred practice of the present invention. These predeterminedflux densities may also be achieved by conventional devices other thanHelmholtz coils, such as solenoids, electromagnets, and permanentmagnets.

Apparatus 100 generates a predictable, measurable and uniform magneticflux density within active volume 106. This active volume will encompassthe total volume of cells and/or tissue that are exposed to a compositeflux density. A unipolar vector representing the composite magnetic fluxdensity is illustrated by arrows A1 and A2 separated by a "." thatrepresents the average nonzero value of the vector. The opposed arrowsrepresent the fact that the magnitude of the composite magnetic fluxchanges at a predetermined rate; however, as will be explained, thedirection of the flux does not change. For purposes of illustration, asingle exemplary living cell 108 is shown within active volume 106.

Cell 108 contains a specific complement of intrinsic ionic species andis surrounded by a liquid or tissue medium containing ionic speciesrequired for cell and tissue function. TABLE 1 lists a typical, butincomplete, group of such ionic species suitable for use with theinvention and shows the charge-to-mass ratio (q/m) of each species, inunits of Coulombs per kilogram, as well as a preferred repetition rateor frequency (f_(c)), in Hz, for each species, for the specific case inwhich the composite magnetic flux density is 5×10⁻⁵ Tesla. For any otherionic species not indicated in TABLE 1, or for any composite magneticflux density other than 5×10⁻⁵ Tesla, the preferred frequency is foundusing the Cyclotron Resonance Relationship.

                  TABLE 1                                                         ______________________________________                                        Ionic Species                                                                              (q/m), Coulombs per Kilogram                                                                     (f.sub.c), *Hz                                ______________________________________                                        Hydrogen, H.sup.+                                                                          95.6 × 10.sup.6                                                                            761                                           Lithium, Li.sup.+                                                                          13.9 × 10.sup.6                                                                            111                                           Magnesium, Mg.sup.++                                                                       7.93 × 10.sup.6                                                                            63.1                                          Calcium, Ca.sup.++                                                                         4.81 × 10.sup.6                                                                            38.3                                          Sodium, Na.sup.+                                                                           4.19 × 10.sup.6                                                                            33.3                                          Chlorine, Cl.sup.-                                                                         2.72 × 10.sup.6                                                                            21.6                                          Potassium, K.sup.+                                                                         2.46 × 10.sup.6                                                                            19.6                                          Bicarbonate, HCO.sub.3 .sup.-                                                              1.57 × 10.sup.6                                                                            12.5                                          ______________________________________                                         *Resonance frequency at 5 × 10.sup.-5 Tesla.                       

Coils 102 and 104 are energized by controller 105 to generate a magneticflux density within active volume 106 that varies with time as shown inFIG. 2 of the drawings. A nonzero average magnetic flux density, uniformthroughout the active volume, results either from an offset sinusoidalsignal or from a full-wave rectified signal applied to coils 102 and104.

The local constant magnetic flux density will in general be superposedon the applied magnetic flux density generated by coils 102 and 104 inactive volume 106. The local flux density which will generally comprisethe geomagnetic field, will have one component along the direction ofthe Z-axis. Hence, the effect of the Z-component of the local fluxdensity will be to change the nonzero average magnetic flux densitycreated by coils 102 and 104 within active volume 106 to a different netaverage value, the value of the resultant composite magnetic field i.e.the combined local and applied field along the Z-axis.

Apparatus 100 further includes a magnetic field sensing device, shownhere as magnetometer 110 which is positioned in coil 102 to measure thetotal or composite magnetic flux which passes through predeterminedspace 106 parallel to the predetermined Z-axis. It will be understood,then, that magnetometer 110 is provided to measure the compositemagnetic field along the Z-axis. Magnetometer 110 then sends a signal tocontroller 105. As stated, the local field component either augments ordecreases the applied magnetic flux unless the local field component iszero. The presence of the local field is an important consideration inthe present invention. The relatively low applied flux densities andrelatively precise predetermined relationships of combined flux densityand frequency provided by the present invention must be maintained,notwithstanding the influence of the local magnetic field. This isachieved in essentially two preferred manners which will be explainedmore fully herein. Thus, magnetometer 110 is provided to determine themagnitude of the magnetic flux density of the local magnetic field.

Hence, in one embodiment of the invention, predetermined space 106 isoccupied by living cell 108 and a preselected ion. Predetermined Z-axiswhich projects through predetermined space 106 and thus through livingcell 108 is defined by the relative position of apparatus 100 withrespect to cell 108. Predetermined Z-axis is the direction of theapplied magnetic flux generated by field coils 102 and 104 throughpredetermined space 106. During this procedure, magnetometer 110measures the total magnetic flux density parallel to the Z-axis whichpasses through cell 108. This total or composite magnetic flux densityis the sum of the applied component and the local component. The localcomponent may at times be in the same direction as the applied flux andat other times be in directions other than the applied flux. At timesthe local component may drop to zero.

Thus, changes in the local component along the Z-axis may be produced bychanges in the direction of apparatus 100. Thus at T₁ the applied fluxgenerated by field coils 102 and 104 may be parallel to a north-southaxis and since the direction of predetermined Z-axis is defined by thedirection of the applied flux, in this position, predetermined Z-axis istherefore also in the north-south direction. At T₂, apparatus 100 may beturned to the north causing a 90 degree rotation of field coils 102 and104 such that the applied magnetic flux is then parallel to an east-westaxis. Accordingly, predetermined Z-axis is then also in the east-westdirection. In most cases, the local component of interest will have avalue which is a function of directions. Therefore, the composite fluxmeasured by magnetometer 110 along the predetermined Z-axis will changein response to changes in the position of apparatus 110 with respect tothe local magnetic field. The net average value of magnetic flux densityis accordingly regulated to compensate for the change in composite flux.

Transmembrane ion transport is achieved by creating a fluctuatingcombined or composite magnetic field having a magnetic flux densityparallel to predetermined Z-axis, where the combined magnetic fluxdensity along the Z-axis is maintained at a predetermined relationshipto the frequency of the fluctuations. The combined magnetic flux densityparallel to the Z-axis has a non-zero net average value. As illustratedin FIG. 2 of the drawings, the composite magnetic field of the presentinvention can be thought of as a static field having reference level "A"on which a fluctuating magnetic field is superimposed. It comprises anac component which varies in amplitude but not direction and a dcreference around which the ac component varies. Reference level A is thenon-zero average value of the flux density. Therefore, it will beunderstood that the non-zero average or net average value of thecomposite magnetic flux density along the Z-axis is utilized since themagnitude of the composite flux density changes at a predetermined ratedue to oscillation or fluctuation of the applied magnetic flux. Thisreflects the fact that although the composite magnetic flux densityalong the axis is oscillating at a controlled rate, the composite fieldis regulated by the intensity of the applied field to ensure that thecomposite field is always unipolar; that is, the composite field isalways in the same direction along the Z-axis.

As stated, it has been found that rather precise relationships of theflux density of the combined magnetic field to the frequency of thefluctuations are used in the present invention to regulate transmembraneion transport. These ratios of frequency to composite flux density arefound in accordance with the following equation:

    f.sub.c /B=q/(2 πm)

where f_(c) is the frequency of the combined magnetic field in Hertz, Bis the net average value of the magnetic flux density of the combinedmagnetic field parallel to the Z-axis in Tesla, and q/m has a value offrom about 5×10⁵ to about 100×10⁶ Coulombs per kilogram. B preferablyhas a value not in excess of about 5×10⁻⁴ Tesla. By exposing cell 108 toa regulated magnetic flux density having these characteristics, thepredetermined ion is transported through cell membrane.

It will be appreciated by the prior explanation of preferred embodimentsof the present invention and from the equation for establishing acyclotron resonance relationship, that either the frequency of thefluctuating magnetic field or the magnitude or intensity of the magneticflux density along the predetermined axis, or both the frequency and theintensity of the flux density, can be adjusted to provide a magneticfield within volume 106 which has the desired characteristics. However,as stated, it is preferred to maintain a constant frequency which thusrequires that the intensity of the applied magnetic flux density beadjusted to compensate for changes in the local magnetic field in orderto maintain a constant ratio of frequency to magnetic flux density. Forexample, if it necessary to maintain a frequency of 15 Hz and an averageflux density of 1.95×10⁻⁵ Tesla to affect ion transport, changes in thelocal field which would otherwise cause unwanted deviations in thecombined magnetic flux density must be corrected by increasing ordecreasing the applied magnetic flux density accordingly. This isperformed by a microcontroller in controller 105 in connection with boththe field generating means and the field-sensing device. Alternatively,as stated, if changes in the combined magnetic flux density along theaxis will occur due to changes in the orientation of apparatus 110 withrespect to the preexisting local magnetic field, the frequency of theoscillations can then be changed so that the preferred ratio ismaintained. It will be understood that detection of changes in themagnetic field due to changes in the ambient component should be atintervals frequent enough to provide a frequency-to-magnetic field ratiowhich is substantially constant, notwithstanding the changes in thelocal field component.

It may also be appropriate in some instances to reduce components of thelocal magnetic field which are not parallel to the axis to zero throughthe use of additional coils positioned at right angles to coils 102 and104 to create an opposite but equal field and that one coil of eachadditional coil pair may be equipped with a magnetometer, although thisis not deemed necessary. It may also be suitable to reduce the localmagnetic field component to zero along the Z-axis using additional coilsor the like.

Referring now to FIG. 3 of the drawings, a block diagram is shown whichdepicts one preferred arrangement of the circuits of apparatus 100 infunctional segments. Numerous other circuit arrangements may be possibleif the principles of the present invention are faithfully observed.Microcontroller or microprocessor 200 is seen by which the compositemagnetic field is maintained at a constant predetermined level despitechanges in the ambient component as previously described. In thisrespect, input 202 is provided by which a set point value of thepredetermined composite magnetic flux density along a predetermined axisthrough the membrane is input into microprocessor 200. As will be shown,the composite field strength is compared to this set point value togenerate an error equal to the difference in the set point value and themeasured value of the composite magnetic flux density along the axis.

As stated, a magnetic field sensor, shown here as block 204, is providedby which the magnitude of the composite field which passes through cell108 along the Z-axis is measured. It is preferred that magnetic fieldsensor 204 comprise a Hall-effect device which, as will be known bythose skilled in the art, produces an analog signal. The magnetic fieldsensor 204 constantly monitors the composite magnetic field, sending asignal to microprocessor 200. It will be understood that the output of aHall-effect magnetic sensor is relatively small; thus, magnetic fieldsensor amplifier 206 is provided by which the signal from magnetic fieldsensor 204 is amplified, for example, up to three thousand times itsoriginal value. Since a Hall-effect device produces an analog signal,analog-to-digital converter 207 is provided by which the amplifiedsignal from magnetic field sensor 204 is converted to a digital signalwhich can be used by microprocessor 200. It is preferred that theanalog-to-digital converter be provided onboard the microprocessor chip.

As will be appreciated, the amplification of the magnetic field sensorsignal may produce an unwanted noise level. Also, sudden changes in themagnetic field intensity may occur which make it difficult to determinethe true average value of the composite magnetic flux density. Hence,the signal from analog-to-digital convertor 206 which is input intomicroprocessor 200 is filtered by software filter 208 to remove shotnoise and sudden fluctuations in the composite field detected bymagnetic field sensor 204. Although it is preferred that filter 208comprise software in microprocessor 200, a discrete filter could beused. In this embodiment, software filter 208 is a digital filter,preferably an integrator with a time constant of approximately 0.5seconds. In other words, the changes in the magnitude of the compositemagnetic field which are compensated for by increasing or decreasing theapplied field are long-term changes of 0.5 seconds or more which resultprimarily from changes in the orientation of apparatus 100 with respectto the ambient field component. Hence, the time constant of filter 208should be such that momentary fluctuations are filtered out.

Microprocessor 200 includes logic which calculates the non-zero netaverage value of the composite magnetic flux density. This non-zeroaverage value is then compared at comparator 210 in microprocessor 200to the predetermined dc reference or offset value which is input intomicroprocessor 200 via input 202. It should be noted that this referencevalue is preferably established by dedicated circuitry in microprocessor200, although variable input means could be included by which the setpoint value could be changed. An error statement is then generateddefining the difference in the measured value of the composite magneticflux density and the set point or reference value. Microprocessor 200then determines the magnitude of the output necessary to drive magneticfield generating coils, shown here as block 212, to bring the compositemagnetic flux density back to the set point W and produces a signal toincrease or decrease the magnetic flux density.

Software field modulator or oscillator 214 is provided by which an ac orfluctuating component is superimposed on the digital output signal whichis input into digital-to-analog converter 216. From the previousdiscussion of the present invention, it will be understood that softwarefield modulator 214 of microprocessor 200 in the preferred embodiment ofthe present invention is preset to a fixed, predetermined frequency toproduce the desired predetermined, ion transport ratio offrequency-to-magnetic flux density value. In another embodiment, thefeedback system of the present invention is such that changes in thecomposite magnetic flux density are measured, whereupon microprocessor200 determines the necessary change in frequency to maintain thepredetermined relationship. In that embodiment, software field modulator214 produces the requisite ac frequency. It is again preferred thatdigital-to-analog converter 216 be provided on-board the microprocessorchip. Hence, software field modulator 214 provides the ac component atnode 218.

The signal from digital-to-analog converter 216 is fed tovoltage-to-current amplifier 220, the output of which drives magneticfield generating coils 212 in the desired manner. Hence, the compositefield is held substantially constant despite changes in the ambientcomponent.

While several arrangements of power sources are suitable, it ispreferred that power supply 222 be provided to power magnetic fieldsensor amplifier 206, microprocessor 200 and magnetic field sensor 204,the latter via bias circuitry 224. A separate power source 226 ispreferred for voltage to current amplifier 220.

Having fully described the apparatus of the present invention, includingits manner of construction, operation and use, the method of the presentinvention will now be described. It is to be understood that thisdescription of the method incorporates the foregoing discussion of thenovel apparatus. In this aspect, the present invention provides a methodof regulating the transmembrane movement of a preselected ion across abiochemical membrane such as the cell membrane of a living cell. This isachieved in one embodiment by generating a fluctuating,directionally-oriented magnetic field which projects through the targetbiochemical membrane. A number of magnetic field generating means aresuitable for this purpose. The magnetic field so generated has amagnetic flux density of precisely controlled parameters which passesthrough the target membrane parallel to a predetermined axis projectingthrough the tissue. As will be known by those skilled in art and as hasbeen clearly explained, the local magnetic field to which the membraneis subjected will have a component which is parallel to thepredetermined axis and which thus aids or opposes the applied orgenerated magnetic field along the axis. At times, the local componentmay be zero. In the method of the present invention, the density of thiscombined magnetic flux, and more specifically the average non-zero valueof the combined magnetic flux density, is controlled to provide aprecise relationship between the flux density along the axis and thefrequency of the applied magnetic field which is oscillating at apredetermined value. Most preferably this is accomplished byautomatically adjusting the intensity of the applied field to compensatefor changes in the local field. Thus, in one embodiment, the presentinvention provides a method of regulating transmembrane movement of apreselected ion by creating a magnetic field which penetrates the targetmembrane and which has a predetermined relationship between frequency ofoscillation and average flux density. The predetermined relationship orratio of frequency-to-field magnitude is determined with reference tothe equation:

    f.sub.c /B=q/(2 πm)

where f_(c) is the frequency of the combined magnetic field along thepredetermined axis in Hertz, B is non-zero net average value of themagnetic flux density of the combined magnetic field parallel to theaxis in Tesla, q/m is in Coulombs per kilogram and has a value of fromabout 5×10⁵ to about 100×10⁶. B preferably has a value not in excess ofabout 5×10⁻⁴ Tesla.

In order to create a fluctuating magnetic field having the desiredparameters, the composite magnetic field parallel to the predeterminedaxis is constantly monitored. As stated, this is preferably carried outwith a Hall effect device or the like which produces an analog signal.This analog signal is periodically sampled by microprocessing meanswhich then calculates the necessary frequency and/or magnitude of theapplied magnetic field to maintain the preprogrammed, predeterminedratio previously described. Of course, it will now be understood that itis the combined magnetic flux which is sensed by the magnetic fieldsensor. The magnetic field generating means is used to adjust themagnitude of this composite field where appropriate.

In one embodiment, the method includes controlling the average value ofthe applied magnetic flux density along a predetermined axis to maintaina predetermined ratio of frequency-to-composite magnetic flux density.In another embodiment, the frequency of the fluctuations is adjusted tomaintain this relationship in which changes in the combined magneticflux density due to changes in the local magnetic field are detected.Moreover, a combination of these two methods may be used wherein boththe frequency and the magnitude of the magnetic field flux density areadjusted to maintain the predetermined relationship of the presentinvention.

Hence, in addition to the apparatus of the present invention, thepresent invention provides a method for controlling transmembranemovement of a preselected ion across a biochemical membrane whichincludes the steps of creating a fluctuating magnetic field ofpredetermined frequency and flux density along an axis projectingthrough a predetermined volume and positioning a target biochemicalmembrane such as a living cell within this predetermined space such thatit is exposed to the fluctuating magnetic field. The predeterminedparameters of the fluctuating magnetic field are determined by measuringthe net average value of the combined magnetic flux density parallel tothe predetermined axis through the tissue, where the combined magneticfield is the sum of the local magnetic field along the predeterminedaxis and the applied magnetic field with a magnetic sensing means. Thefrequency and/or magnitude of the applied magnetic flux density is thenautomatically controlled by a microprocessor to produce a combinedmagnetic field along the axis having a predetermined ratio offrequency-to-flux density. This predetermined ratio causes transmembranemovement of the preselected ions.

While particular embodiments of this invention are shown and describedherein, it will be understood, of course, that the invention is not tobe limited thereto, since many modifications may be made, particularlyby those skilled in the art, in light of this disclosure. It iscontemplated, therefore, by the appended claims, to cover any suchmodifications as fall within the true spirit and scope of thisinvention.

What is claimed is:
 1. An apparatus for enhancing the transfer of apredetermined ion having a predetermined charge-to-mass ratio through amembrane located in a space subjected to a local magnetic field, thespace defining at least one reference path passing through the membrane,the reference path extending in a first direction and also extending ina second direction opposite the first direction, said apparatuscomprising:field creating means responsive to signals for creating amagnetic field which, when combined with the local magnetic filed,results in a resultant magnetic field having a flux density with atleast one component representable by a component vector having adirection extending in the first direction along the path and having amagnitude that fluctuates at a predetermined rate to create a nonzeroaverage value, the ratio of the predetermined rate to the nonzeroaverage value having a predetermined relationship which is a function ofthe charge-to-mass ratio of the predetermined ion; signal generatingmeans for generating said signals, at least some of said signals beinggenerated at the predetermined rate; magnetic sensing means adapted tomeasure a magnetic flux density having a nonzero average value formeasuring the magnitude of said one component of said resultant magneticfield; and means in association with said field creating means forautomatically adjusting the magnitude of said one component of saidresultant magnetic field to maintain said predetermined relationship. 2.The apparatus recited in claim 1, wherein said magnetic sensing meansincludes a Hall-effect device.
 3. The apparatus recited in claim 2,wherein said automatically adjusting means includes a microcontroller.4. An apparatus for the transmembrane movement of a preselected ion,comprising:a pair of field coils for generating an applied magnetic fluxin a predetermined space and parallel to a predetermined axis whichprojects through said predetermined space, said predetermined spacebeing occupied by a biochemical membrane and a preselected ion; amagnetic field-sensing device adapted to measure a magnetic flux densityhaving a nonzero average value for measuring magnetic flux densityparallel to said predetermined axis in said predetermined space; andmicroprocessing means, including means for oscillating said appliedmagnetic flux, in communication with said field coils and saidfield-sensing device for creating and automatically maintaining apredetermined relationship which is a function of the frequency of saidmagnetic field and the intensity of said magnetic flux density toprovide a fluctuating magnetic field which causes transmembrane movementof said preselected ion through said biochemical membrane.
 5. Anapparatus for enhancing the transfer of a predetermined ion having apredetermined charge-to-mass ratio through a membrane located in a spacesubjected to a local magnetic field, the space defining at least onereference path passing through the membrane, the reference pathextending in a first direction and also extending in a second directionopposite the first direction, said apparatus comprising:field creatingmeans responsive to signals for creating a magnetic field which, whencombined with the local magnetic field, results in a resultant magneticfield having a flux density with at least one component representable bya component vector having a direction extending in the first directionalong the path and having a magnitude that fluctuates at a predeterminedrate to create a nonzero average value, the ratio of the predeterminedrate to the nonzero average value having a predetermined relationshipwhich is a function of the charge-to-mass ratio of the predeterminedion; signal generating means for generating said signals, at least someof said signals being generated at the predetermined rate; magneticsensing means adapted to measure to flux density having a nonzeroaverage value for measuring the magnitude of said one component of saidresultant magnetic field; and means in association with said fieldcreating means for automatically adjusting the frequency of saidfluctuation to maintain said predetermined relationship.
 6. Theapparatus recited in claim 5, wherein said magnetic sensing meansincludes a Hall-effect device.